Conventionally, for conducting machining such as polishing or cutting on semiconductors, metals and so on, a slurry in which abrasive grains or polishing grains are suspended is used. However, as the machining progresses, not only removed powder generated from the processing object, but also abrasion powder of an apparatus used in machining, for example, magnetic material particles generated by abrasion of a surface plate or a wire saw are mixed in the slurry, leading to a problem of a significant deterioration in machining accuracy. Therefore, conventionally, the slurry needs to be replaced regularly, and the used slurry is treated as industrial waste.
Diamond and the like that are precious resources are used as abrasive grains or polishing grains, and silicon and the like that are precious resources are also used as processing objects. These resources will run short in the future. Hence, for solving the shortage of resources, recycle of slurry and further recycle of abrasive or polishing grains or removed powder generated from processing objects is suggested.
For the realizing recycle of a slurry or the like, it is necessary to remove magnetic material particles from the slurry (slurry-like mixture) used in machining, and it is conceived to remove magnetic material particles from a slurry-like mixture using, for example, the magnetic separator disclosed in Patent document 1.